Pneumonia is the leading cause of hospitalization of HIV-positive adults in Soweto, South Africa, where 30% of the population is HIV-positive. Streptococcus pneumoniae is implicated in the etiology of up to 46% of pneumonia episodes in HIV-positive adults in Africa, and the 23-valent pneumococcal vaccine appears ineffective and possibly deleterious to the health of African HIV-positive adults not receiving antiretroviral therapy. Data from a recently completed prospective randomized trial of a conjugate pneumococcal vaccine among 39,836 children in Soweto has demonstrated a 72% efficacy of this vaccine in preventing vaccine type invasive pneumococcal disease (IPD) and a 17% reduction in all pneumonia in these children. A similar vaccine, given to children in the United States, has recently been demonstrated to reduce IPD in adults by means of a herd immunity effect. The vaccine is thought to interrupt transmission of vaccine serotypes (pediatric serotypes) from children to adults. The effectiveness of this approach to prevent IPD (and possibly non-bacteremic pneumococcal pneumonia) depends on the fraction of pediatric serotypes causing invasive disease in adults. [unreadable] [unreadable] The research team has demonstrated that conjugate pneumococcal vaccines interrupt transmission of pediatric serotypes in children in Soweto. It has also shown there to be a significantly increased risk of pediatric serotypes causing IPD in HIV-positive adults (and particularly in women) in Soweto. This proposal's objective is to determine whether pneumococcal conjugate vaccination of infants will reduce the burden of pneumococcal disease in HIV-positive women. This objective will be met by first (Specific Aim 1) investigating retrospectively whether IPD and pneumonia were reduced in the mothers of 19,922 children vaccinated compared to 19,914 controls enrolled in the previous pediatric vaccine trial. The extent of herd immunity induced by that trial may, however, be expected to be limited. A prospective study (Specific Aim 2) will ascertain the vaccine preventable burden of IPD and pneumonia in 2,000 adults in the community prior to the routine introduction of pneumococcal conjugate vaccination in infants in order to assess the impact of that intervention on IPD and pneumonia in HIV-positive women. [unreadable] [unreadable]